Evidence is mounting that being overweight isn't as detrimental to one's health as previously believed. In fact, numerous studies conducted on patients with certain chronic diseases found that those who were overweight to moderately obese had a lower mortality rate than those of normal-weight suffering from the same illness. It's being called "the obesity paradox."

For a piece about the phenomenon, the New York Times spoke with several experts that who have met with resistance over research suggesting that obese patients often fare better than thin ones. Dr. Carl Lavie — medical director of cardiac rehabilitation and prevention at the John Ochsner Heart and Vascular Institute in New Orleans — spent a year trying to get his findings about the obesity paradox with regards to heart failure published in a medical journal, saying:

"people thought there was something wrong with the data. They said, ‘If obesity is bad for heart disease, how could this possibly be true?'"

While Dr. Lavie was one of the first to document the obesity paradox in 2002, study after study since then has supported his original findings. For instance, one study found that heavier dialysis patients had a lower mortality rate than normal-weight or underweight patients. Same with a study about coronary disease, diabetes, stroke, and high blood pressure. In 2007, a study conducted on over 11,000 Canadians over the course of a decade found that overweight people had the lowest chance of dying from any cause.

So far scientists are at a loss for the reasons behind the obesity paradox. One theory is that chronic diseases require higher energy and caloric reserves from a body. Another is something called "metabolically obese normal weight," meaning that a patient can have a normal body mass index, but also have metabolic abnormalities like high insulin levels.

Mostly, though, long-held assumptions about body fat and health have only taken B.M.I. into account (which is a ratio of height and weight) and not physical activity or fitness. A person who exercises and weighs more is often healthier than a person who doesn't and weighs less.

But it will apparently take a while for even general practitioners to catch on, as one nutritionist (ironically named) Linda Bacon says that our ideas about weight are "just too culturally embedded, and the risk of going against convention is too high."

That's not to say that you should eat a bacon double cheeseburger and consider it preventative medicine. But the argument that overweight automatically means unhealthy is getting thinner.